Their presence on archaeological sites is used to date the soil layers and the objects and events they are associated with and thus contributes to refine the chronology of sites.
Indeed, some items whose exact or approximate age is known are called "diagnostic artifacts." Examples of such objects include very specific stone tools, different pottery styles, objects that belong to a specific period (eg, the historic period or the French regime), coins with a production date, or other items bearing a trademark and whose history can be traced in historical records.
Generally, each stratum is isolated in a separate chronological unit that incorporates artifacts.
However, this method is sometimes limited because the reoccupation of an area may require excavation to establish the foundation of a building, for instance, that goes through older layers.
This technique is frequently used when it is impossible to make use of absolute dating methods; it generally allows archaeologists to identify the period to which a cultural site or object belongs, without specifying the date of occupation.
This method is primarily applied to projectile points and ceramic vessels.